Landing gear



April 18, 1944- Q J. 'H. STEPHENS 2,346,797 I LANDING GEAR Filed April 16, 1941 3 Sheets-Sheet 1 April 18, 1944. J. H. STEPHENS 2,346,797

LANDING- GEAR Filed April 16, 1941 3 Sheets-Sheet 2 gwuem fom Ap 1944- J. H. STEPHENS 2,346,797 I LANDING GEAR Filed April 16, 1941 3 Sheets-Sheet 3 sense a is. i

GEAR John Harris Stephens,

West orto e Glenn IL. l

Q'Jhester, We assign- Cornpany, Baltimore,

Application April lid, will, Serial No. 3883M (Ci. M lk-m2) 12 Ciaims.

This invention is directed to retractable landing gear for aircraft. More particularly, the invention is directed to the construction of the landing gear, and to novel means for locking the landing gear in down position.

An obiect of the invention is to provide a novel supportfor the oleo strut of a. retractable landing sear.

Another object of the invention is to produce a novelly braced landing gear which is fully retractable;

Another object of the invention is to produce a simple, lightweight landing gear andmeans for fully retracting the some.

Another object of the invention is to produce a novel mechanism for loclfing the landing gear in down position by reason of which drag stresses are taken away from the wheels of the carriage or trolley supporting a portion of the retracting mechanism,

orally these objects of the invention are obtained by fitting the upper end of the oleo strut into a rotatable cross-beam supported between two fixed bearings. A hydraulically operated crank on one end oi this cross-beam serves to rotate the cross-beam to retract the strut. A drag strut has one end attached to the oleo strut while the other end is supported by a trolley which slides upon a track. In the down position of the landing gear the trolley is efiectively lifted from the trach upon a fixed support and locked in place, thus eliminating the transfer of stresses through the trolley wheels to the track. The construction is quite simple, easily assembled and taken apart for maintenance purposes, and is eiiectively braced against the strains encountered during the landing of aircraft. a

4 The means by which the objects of the invention are obtained are more fully disclosed in the accompanying drawings, in which:

Fig. 1 is a side elevational view of the landing gear;

his. 2 is a front elevational view oi the landing gear;

tion oi the locking mechanism for locking the landing gear in down position;

his. a is a. side view partly, in section showing the trolley on the track in the down position;

Fig. 5 is a cross-sectional view on the line 5-5 oi Fig. i; and

Fig. 6 is a partial plan view of Fig. 4. I The landing gear assembly as shown in Figs. 1 and 2 is composed of an oleo strut 2 from which an extensible arm t projects to hold the canti- Fig. 3 is an enlarged side view partly insets-s leverally supported wheel 6. The upper end oi strut 2 is set in a joint 8 between the ends of a cross-beam ill, the ends 01 which are set in bearings it and it, respectively. These bearings are located on the lowermost points of an N- shaped truss it which is fixed to the frame of the aircraft.

It is noted that joint t is located adjacent bearing it. A fitting it adjacent bearing it supports one end oi a brace 20, the lowermost end of which is attached to the strut 2 at 22. Consequently the strut 2 is firmly braced in its attachment to the cross-beam it. By placing the joint t near the bearing 82, wheel 6 is located beneath cross-beam it, thus producing compactness and strength,

Cross-beam it is rotatable in hearings l2 and it. To effect such rotation one end of cross-beam it is pivotally joined at 225 to a crank it which is operatively connected to a hydraulically operating mechanism 2t of the conventional type, one end of which is attached to the frame of the aircraft by a pivotal connection iii.

A drag strut so is pivotaliyattached at its lower end at to strut 2 while its upper end is pivotally attached at it to a carriage or trolley 35 mounted upon a track to as will be later described.

Also attached to opposite sides of strut 2 are arms db and d2, respectively, for mechanically operating the trap doors which are pulled up to close the opening beneath the landing gear when it is in its retracted position. Also shown in Fig. 2 is the up position loch dd mounted upon the aircraft frame, this look engaging a lug or other means on strut 2 when the landing gear is in retracted position.

Because of the construction so far described, vertical shocks upon strut 2 are transmitted through cross-head it to truss it and distributed to the frame of the aircraft, while at the some time the use of the cross-head it permits a very simple means for rotating the strut into retracted position. It is clear that when the hydraulic mechanism 2b is operated the crank to will be rotated counterclockwise in Fig. i to cause the strut to move into its retracted position. llturing this operation, trolley dd supporting the upper end of drag strut dd is moved to the right hand side of track to. By reason of brace 2t, wheel it lies directly below cross-head it in the down position of the gear, while strut 2 is braced against twisting and transverse displacement.

When the landing gear is in down position the gear must be locked in position, and this is done by the down gear lock to shown generally in from the track.

Fig. 1 and in more detail in Figs. 3 to 6. inclusive. a feature or this locking construction lies in relieving the wheels of the trolley 88 from the stresses produced upon drag strut 30 in lending and transmitted through the trolley to the track.

The down position lock 50 is composed oi a hydraulic cylinder in which moves a piston normally urged downwardly by means of a spring. To this piston is connected as plunger 52, the lower end Bl of which is beveled and provided with a bore 56 adapted to receive a locking pin 88.

Track 38 is in the form of a double channel the flanges which are trackways, and has a solid end portion 80 in which a bore 62 receives the pin 58 and a spring 66 urging the pin into locking position with the plunger 52, a vertical passageway 88 in portion 80 being aligned with plunger 52 for the reception of the same. At the end of the. track, the track flange portions 88a and 3% are spread so that the distance between them is greater than the diameter of the wheels on the trolley.

' l brward movement of the pin d8 is restricted by a flange 68 hearing against a shoulder Id in the bore. The rear end of pin 58 passes through a plug I! screwed in and closing the rear end of bore 62, and is united in any conventional manner to a cross-piece Il'whlch extends transversely beyond the sides oi the traclrway Q8. De pending from solid portion 60 is e. hook-like member 18 which hmctions to support the carriage or trolley as will be presently described.

The trolley or carriage 86 is composed of a solid arm 80 pivotally joined at St to drag strut 38. From member 80 two arms 82a and 822 err-- tend to opposite sides of track 38, note Fig. Each of these arms is substantially oi Y-shape and has wheels 84 mounted at each free end of the Y, each wheel being supported by a shaft resting in an appropriate bearing in the end of its respective Y arm. The rearmost extending Y arm 83 is continued into a projection 86 which,

as the carriage moves to the left, compar Figs. 3 and 4, contacts the cross-member l5 and moves it rearwardly.

Between the arms 88c and b a substantially rectangular'block 88 is fastened by means 0! a shear pin so. A second pin 91 passes through a bore in block 88 or greater diameter than the pin to prevent arms 82a and 82!! from spreading and to hold block as in horizontal position but with sumcient movability so that it can adjust itself into the recess between tongue I6 and the bottom oi section 80. The forward end it of block 88 is sllghtLv beveled as shownin Fig. 4.

The operation or this locking mechanism is as follows: As the landing gear is moved-to down position the trolley 38 moves to the left from the-posltion shown in Fig. 3 to that of Fig. 4. The trolley when reaching the end or its travel brings the projection 8t into contact with the cross-member H and moves the eroswmembe together with the pin I8. As shown in Fig. 4 pin As the trolley is moved toward the left member so becomes flrmly seated, upon the boob-like member 16, it being noted that the plunger 82 exercises a wedging action against bevel face as at block 88 to force block' 88 into the recess beassets? In so being seated the trolley, including the wheels 84. is lifted from the track so that all stress transmitted by drag strut to track it is through the hook member and the base oi the track rather than through wheels as. As member 88 is seated upon hook member I! at the same time that pin 58 is withdrawn from hole Bl to release plunger 52. the plunger will fall down-. wardly and bear against the front face ll of member 88 to lock the trolley in place.

When the landing gear is to be retracted, fluid pressure is applied to cylinder to raise the piston therein and thus raise plunger 62 to unlock trolley so. At thesame time fluid pressure in cylinder 2s causes crank 24 to be actuated so that the landing gear starts to retract, and as the trolley 38, moves to the right, Fig. 4, the spring as pushes pin 58 to enter into hole II in plunger 52 to lock the plunger in its up position. As the plunger is locked in its up position, there is no chance of it dropping and preventing the trolley from moving into the full down positio oi the landing gear.

It is thus apparent that the invention pr vides asimple, compact, easily assembled, strong and well braced iully retractable landing gear, including a means for preventing stresses from being transmitted to the wheels of the trolley through the drag strut, and means for locking the trolley in. the down position or the landing gear.

Having now "disclosed the means by which the objects of the invention are obtained, I claim:-

I. A retractable landing gear for aircraft comprising a rigid structure, an oleo strut adapted to carry a wheel, said strut being rotatably mounted on said structure, a retractingmechanism adaptare capable of being lifted ed to rotate said strut and wheel about an axis within said structure, a track-waymounted on said rigid structure, a drag strut. one end of said drag strut being adapted to ride on said trackway, the other end of said drag strut adapted to be pivots-11y secured to the said oleo strut at a point near the intersection of said oleostrut with a wheel, a load bearing structural member adjacent the said track-way in which a portion of said drag strut is wedged when the landing gear is in extended position, a locking element forming a part of said structural member, means rendered operative by the movement 01' said drag strut along said track-way, said locking element adapted to wedg'edly secure the said drag strut to the said structural member when the landing gear is in down position, and means whereby said locmng element is automatically disengaged by the operation of the retracting mechanism. 4

2. In a retractable landing gear for an airplane having the conventional oleo strut-supported wheel, a drag strut, a track adapted to receh'e and guide said drag strut retracting mechanism and an lip-lock; a down-lock comprising a hook-like member adapted to receive a portion oi said drag strut, said hook-like member which forms a part of the direct load bearing structure beingrlgidly secured to said track at the point oi intersection oi. said track with a direct load bearing structure.

3. a retractable landing gear for aircraft comprising an oleo strut supported wheel, a. drag strut, a track adapted to receive a portion of said drag strut, a retracting mechanism adapted to raise and lower said wheel by turning said wheel aboutan axis within the structure of the airplane, and a downlock adjacent said track and forming a. part of the load bearing'structure oi prising a drag strut, a track for guidin the airplane, said down-lock adapted to receive and have securely wedged therein a portion of said drag strut and means rendered operative by movement of said drag strut along said trackway for wedging and locking said portion of said drag strut in said downlock structure.

4. A down-lock for airplane landing gears comprising a drag strut assembly, a track for guiding movement of said drag strut assembly, a load bearing structural member adjacent said track and adapted to receive a portion of said drag strut assembly when same is in down position, and means rendered operative by the drag'strut assembly when riding on said track into said structural member for wedging and locking said drag strut assembly to said member whereby all stress in said drag strut is transmitted to said member and no stress is transmitted to said track.

5. A down-lock for airplane landing gears comgmovement of said drag strut assembly, a load bearing structural member secured to said track at a point adjacent the intersection of said member strut on entering said structural member for wedging and locking said drag strut to said member whereby all stress in said drag strut is transmitted to said member and no stress is transmitted to said track.

6. A down-lock for airplane landing gears comprising a drag-strut, a track for guiding movement of said drag strut assembly, a load bearing structural member forming a part of said track and adapted to receive a portion o said drag strut when same is in the down position, means rendered operative by the drag strut when riding on said track into said structural member for locking said drag strut to said member independently of said track, and means for releasing said drag strut from said member.

'7. A down-lock for airplane landing gears of the conventional retractable type comprising a drag strut, a track for guiding movement of said drag strut assembly, a structural member contiguous with said track adapted to receive a portion of said drag strut when the landing gear is in the extended position, and an automatic locking means forming a part of said structural member for wedgin -and rigidly securing the said portion of said drag strut to said structural member when the landing gear is moved into the down position, whereby the stresses in said drag strut are transmitted to said structural member, leaving said track free from drag strut stresses. I 8. A down-lock for a rplane landing gears of the conventional retractable type comprising a drag strut, a track for guiding movement of said drag strut assembly, a structural member reinforcing a portion oi' said track and forming a part thereof adapted to receive a portion of said drag strut when the landing gear is in the extended position, automatic locking means forming a part of said structural member for rigidly securing the said portion of said drag strut to said structural member when the landing gear' is moved into the down position, and a means for releasing said locking means when it is desirable to retract the landing gear.

9. A down-lock for airplane landing gears of the conventional retractable type comprising a drag strut, a track for guiding movement of said drag strut assembly, a structural member supporting said track at one end thereof and adapted to receive a portion of said drag strut when the landing gear is in the down position, an automatic locking means forming a part of said structural member for wedgedly securing the said portion of said drag strut to said structural member when the landing gear is moved into the extended position, and a lock releasing means cooperating with the landing gear retracting mechanism for simultaneously releasing said down-lock when it is desired to retract the landing gear.

10. A down-lock for a landing gear of the fully retractable type comprising a track, a drag strut adapted to ride on said track, a main load bearing structural member forming an intersection with said track, said drag strut having a portion adapted to be wedged into said structural mem ber adjacent the point of intersection of said track and said member, said structural member adapted to receive the said portion of said drag strut and locking means forming a part of said structural member and rendered operative by said drag strut for securing said strut portion to said structural member, and disengagingmeans for unlocking said locking means when it is desired to retract the landing gear, said disengaging means unlocking said locking means simultaneously and holding same in the unlocked position. i

11. A down-lock for a landing gear of the fully retractable type comprising a track, a drag strut adapted to ride on said track, a main load hearing structural member secure to a portion of said track, said drag strut having a portion adapted to be wedged into said structural member, said structural member adapted to receive said portion of said drag strut and locking means forming a part of said structural member and rendered operative by said drag strut for securing said drag strut to said structural member, and

disengaging means for unlocking said locking means when it is desired to retract the landing gear, saiddisengaging means for unlocking said locking means operated simultaneously with the 6 retracting mechanism.

12. In the retractable landing gear for an airplane having the conventional oleo strut-supported wheel, a drag strut, a track for guiding said drag strut, retracting mechanism and an 'uplock; a downlock comprising a structurally re- 50 said reinforced section, means for pressing said plunger towards its locking position, and a tripping mechanism forming a part of said reinforced section and arranged to release said plunger and wedge said part in said reinforced section, and means carried by the strut for operating said tripping mechanism as it moves along the track during the extension of the landing 7 JOHN HARRIS STEPHENS. 

